This invention relates to the field of marine transport and more specifically to barge cargo transport. In particular, the present invention relates to connected or articulated tug and barge units, also known as articulated pusher boat and barge units.
Articulated tug and barge units have long been used to transport various types of cargo in oceans, rivers, lakes and harbors. A conventional articulated tug and barge unit is commonly coupled together through the use of a ram assembly that extends from the tug into a cavity within a stern notch of the barge. As is shown if FIGS. 1 and 2, tug 14 enters stern notch 12 of barge 10. Vertical channels or receivers 18 are bilaterally mounted within stern notch 12. Upon entry into stern notch 12, a pair of axially aligned rams 16 are extended from opposite sides of tug 14 into channels 18 to provide a virtually unbreakable connection between tug 14 and barge 10. Limiting the relative movement between the tug and barge to only one degree of freedom upon coupling significantly reduces the potential for damage to both the tug and the barge and also increases the ability of the tug to control the barge. Therefore, most ram assemblies of the type shown in FIGS. 1 and 2 provide for relative pitch movement between the tug and the barge while at the same time preventing any relative roll and yaw movement between the tug and the barge.
One prior art ram assembly for mounting on tug 14 is shown in FIGS. 3 through 5. The operation of the particular coupling unit shown in FIGS. 3 through 5 is fully discussed in U.S. Pat. No. 4,688,507 to Kuhlman, et al., the disclosure of which is incorporated herein by reference. Referring to FIG. 3, each receiver or channel 18 is a cast member which is recessed into hull 20 surrounding stern notch 12 of barge 10 (FIG. 2). Each channel 18 has fore and aft walls which converge slightly as they extend inwardly. Flat base 26 connects the walls. Each wall is provided with a series of teeth which are spaced uniformly apart along the entire length of the channel. The teeth are equal in size and are uniformly spaced to balance the forces that are applied and minimize multiple angle planes of contact.
Coupling units 16, which are installed on the opposite sides of tug 14, are identical to one another. Each coupling unit includes cylindrical housing 30 formed of rolled steel plate and having a wall thickness sized to provide considerable strength and rigidity. A pair of circular mounting flanges 32 are welded or otherwise secured to the outer surface of housing 30 and are reinforced by gusset plates 34. Flanges 32 are welded or otherwise suitably connected in rigid fashion with hull 36 of tug 14. Flanges 32 can be suitably spaced to conform with the hull configuration. In this manner, each housing is mounted on the side of tug 14 with the open end of the housing facing outwardly.
Each housing 30 receives a ram which can be extended out of, and retracted into, the housing. Rams 38 are in axial alignment with one another. Each ram has a cylindrical wall which is preferably formed of steel. Ram 38 is carried in cylindrical bushing 40 which is fitted in the outer end portion of housing 30. The bushing provides a large bearing surface and permits the ram to extend and retract as necessary. Bushing 40 has a cavity which receives a packing arrangement 42 formed by a plurality of packing rings. The packing contacts housing 30 and ram 38 to prevent the entry of sea water and other contaminants.
As best shown in FIGS. 3 and 4, the leading or outer end of each ram carries a head which is formed by cast component 44 mounted on a solid steel ball. Ball 46 has neck portion 48 which is welded or otherwise secured to annular flange 50 projecting inwardly from the wall of ram 38. A plurality of gusset plates 52 serve to reinforce ram 38 and its connection with the head.
The opposite sides of head 44 are tapered to conform with the taper of the fore and aft walls of channel 18. The tapered sides of the head are each provided with a plurality of teeth having the same size and spacing as the teeth on the walls of the channel. When the head of each ram is extended into the channel, ram teeth 54 mate with the channel teeth to prevent the heads of the rams from moving vertically within the channels.
Head 44 is mounted on ball 46 for limited pivotal movement about mutually perpendicular axes. Ears 56 project outwardly from flange 50 and receive axially aligned guide pins 58 which are secured to the ears by screws 59. Guide pins 58 project inwardly from ears 56 and are received in bushings 60. Bushings 60 are in turn closely received in slots 62 which are formed in the top and bottom portions of head 44 and which are generally parallel to the ram axis. Split retainer ring 64 retains head 44 on ball 46 and is secured to the head by screws 66.
Guide pins 58 establish a vertical axis about which head 44 can pivot in limited fashion on ball 46. The inside surface of head 44 contacts beveled surfaces 70 on the front face of ball 46 to limit the pivotal movement of the head in both directions about pins 58. The fit of bushings 60 in slots 62 permits head 44 to similarly pivot in limited fashion about a horizontal axis. The front face of ball 46 is provided with beveled surfaces 70 which limit the extent to which head 44 can pivot on the ball about the horizontal pivot axis. Both the horizontal and vertical pivot axes for the head pass through the center of ball 46. The close fit of bushings 60 in slots 62 assures that the head cannot rotate on the ball about an axis coincident with the longitudinal axis of ram 38. Consequently, rotational movement of ram 38 about its axis is transferred by guide pins 58 to the head 44. Lubrication passages 72 extend through ball 46 to provide lubrication.
Ram 38 is extended and retracted by a large, solid, actuator shaft or screw 74 having external threads 76. Screw 74 extends along the axis of ram 38 and is supported for rotation by roller bearings 78 and 80 and by a large spherical roller thrust bearing 82 which receives the end of the actuator screw. Bearings 80 and 82 are located adjacent to one another and are retained within tail section 83 of gear box 84. Gear box 84 is secured to housing 30 and essentially forms a continuation thereof Circumferential flanges 86 and 88 are formed on the adjacent ends of gear box 84 and housing 30, respectively. The outer edge of retainer plate 90 is sandwiched between flanges 86 and 88. Plate 90 and flanges 86 and 88 are secured together by screws (not shown) or in any other suitable manner. Bearing 78 is mounted to retainer plate 90.
With reference to FIG. 4 in particular, actuator screw 74 extends through ring 92 having internal threads that mate with external threads 76 of the screw. Ring 92 is formed as an integral part of ram 38 and is connected with the wall of the ram by a pair of apertured plates 94. Actuator screw 74 is received within steel tube 96 which is secured to and projects outwardly from ring 92.
Actuator screw 74 is driven in normal operation by a pair of electric motors, 98 and 100. Motor 98 is a low speed, high torque motor mounted on platform 102 secured to gear box 84. Motor 100 is a high speed, low torque motor mounted on platform 104 secured to the gear box 84.
Low speed motor 98 drives gear reducer 105 having output shaft 106 which connects through pneumatic clutch 108 with pinion 110. Pinion 110 is supported by bearings 112 and drives larger gear 114 which is mounted on the same shaft as pinion 116. Bull gear 118 is mounted on actuator screw 74 and is driven by pinion 116.
Also connected with pinion 110 are a pair of air motors, 119 and 120, which are used for emergency extension and retraction of the ram. Line 124 leads to fitting 126 which supplies air to the clutch. Also connected with pinion 110 is ratchet handle 128 (shown in phantom) which is accessible so that it can be operated manually to rotate pinion 110 in either direction to thereby either extend or retract ram 38. Handle 128 preferably connects with pinion 110 through a conventional ratchet mechanism.
High speed motor 100 includes output shaft 130 which is connected by coupling 132 with pinion 134. Pinion 134 is supported for rotation by bearings 136. Pinion 134 mates with and drives bull gear 118 which is mounted on the actuator screw.
Thrust bearing 82 rests on load cell 138 which senses the load that is applied to actuator screw 74 during extension of ram 38. Load cell 138 is enclosed within tail section 83 of box 84 and engages cover plate 140 of the tail section. The moving parts of coupling unit 16 are provided with lubricant by lubricant pump 142 (see FIG. 4). Supplying lubrication to various portions of the ram assembly is often difficult due to the axial and rotational movement of the ram.
An internally threaded lock nut 144 is threaded onto actuator screw 74 at a location between bearing 78 and ring 92, as best shown in FIGS. 4 and 5. Lock nut 144 is provided with diametrically opposed lugs 146 which are pivotally connected with the rod ends of a pair of pneumatic cylinders 148. Cylinders 148 control lock nut 144 and are pivotally connected at their base ends with ram 38. When the cylinders are retracted, they tighten lock nut 144 against ring 92 and thereby serve as a ram retraction brake to prevent actuator screw 74 from rotating relative to ring 92, thereby preventing axial movement of the ram. When pneumatic cylinders 148 are extended, they loosen lock nut 144 by threading it away from ring 92. In this condition, actuator screw 74 can be rotated relative to the ring 92, thereby permitting axial movement (extension/retraction) of the ram.
The retraction brake can be activated when it is desired to rotate the ram along with the screw. Such rotation of the ram is often necessary to align ram head 44 with channel 18. When the retraction brake is activated, the ram will rotate with rotation of screw 74; the ram will not move axially with respect to the screw during such rotation.
When ram 38 is fully retracted, it trips limit switch 150 having projecting switch arm 152 engaged by the end of the ram in the fully retracted position. A similar limit switch (not shown) is tripped when ram 38 reaches its fully extended position. Another pair of limit switches, 154 and 156 (see FIG. 5), are tripped when ram 38 is rotated in one direction or the other beyond a limiting position relative to housing 30. If ram 38 is rotated in a counterclockwise direction beyond the limiting position, a projecting switch arm of switch 154 is tripped by plate 158 mounted on housing 30. Conversely, if the ram is rotated in housing 30 beyond a limiting position in the clockwise direction, the switch arm of switch 156 is tripped by plate 158. Housing 30 is provided with side access hatches which are normally covered by removable hatch covers 160 secured by screws 161. When hatch covers 160 are removed, access is provided through the exposed hatches to the interior of housing 30 for inspection and/or servicing of the internal components.
The manner of coupling tug and barge units just described provides a secure, dependable interconnection between a tug or pusher boat 14 and barge 10 and offers far greater control and maneuverability over a barge than the previously used methods of attaching tow cables to barges and pulling them through the water. Additionally, the use of a screw type ram assembly provides a much more reliable connection than that of hydraulic extension which is subject to catastrophic failure. Once the connection between tug 14 and barge 10 is achieved, the boat and barge unit is virtually inseparable and capable of tolerating very rough sea conditions. One report on the device shown in U.S. Pat. No. 4,688,507 indicated that a boat and barge unit coupled by such a device withstood and traveled through a storm having swells in excess of 35 feet.
While this report indicates the strength and durability of this type of extended screw ram assembly to connect a boat to a barge, it will also be appreciated that this type of assembly is quite expensive to manufacture and install on a tug, and adds a considerable amount of weight to the tug.
In the ram assembly of the prior art, high speed motor 100 and low speed motor 98 are used in combination to facilitate the connection between tug 14 and barge 10. When ram assembly 16 is under relatively low load conditions, such as during retraction and during unloaded extension (i.e., prior to contact between head 44 and channel 18), high speed motor 100 is utilized. When ram assembly 16 is subjected to relatively high load conditions, such as when ram head 44 is tightened up against the walls of channel 18 to provide a secure connection, low speed motor 98 will be utilized. An automatic control system that is connected to load cell 138 responds to changes in load on actuator screw 74 to alternate the use of high speed motor 100 and low speed motor 98. The control system energizes one motor, while declutching the other motor. The inclusion of two separate motors and an automatic control system add to both the expense and overall weight of the ram assembly. Therefore, it would be advantageous to provide a ram assembly that eliminates the need for two separate motors.
Another drawback of the prior art just described is that when the ram assembly is extended and brought into tight engagement with channel 18, actuator screw 74 is subjected to a considerable amount of torsion. The torsional force is created by low speed motor 98 which rotates actuator screw 74 to extend ram 38, providing an axial engagement force between the tug and barge. The torsional force is intensified as many tugboat operators tend to increase the engagement force between ram head 44 and the walls of channel 18 to curtail noises caused by slight movements between the respective surfaces of head 44 and channel 18. As the torque applied to actuator screw 74 increases, so does the wear on the components of ram assembly 16. Therefore, it would be advantageous to provide a ram assembly that produces sufficient engagement force without subjecting the actuator screw to substantial torsional forces.
Another disadvantage of the above described ram assembly is present in the design of the ram retraction brake, discussed above. The prior art retraction brake is somewhat complicated, including lock nut 144, cylinders 148 and associated controls, adding to the expense of the assembly. Additionally, engagement of the retraction brake creates continuous torque on actuator screw 74 and causes actuator screw 74 to rotate as ram 38 rotates to the pitch motion of the tug. The continuous torque increases the amount of wear on the actuator screw. The rotation of the actuator screw results in a rotating interface through which the engagement force of ram assembly 16 is transferred from the actuator screw to the hull of the tug boat, thereby increasing wear on the components of the ram assembly. Additionally, the rotation of the actuator screw requires disengagement or declutching of the motors to reduce inertia. Therefore it would be advantageous to provide a ram assembly having a less complicated and non-rotating retraction brake.
The present invention comprises an improved coupler assembly for establishing engagement between a tug or pusher boat and a barge which eliminates many of the disadvantages of the prior art.
It is an important object of the present invention to provide an affordable and lightweight mechanical coupling assembly which has a sufficiently rugged construction to withstand the considerably rugged forces that are encountered. The heavy duty construction of the coupler maintains a positive and secure tug to barge connection under even the worst conditions, thereby eliminating the possibility of hull contact and other dangerous situations.
It is another object of the present invention to provide an affordable and lightweight coupling assembly that significantly reduces the drive force, or torque, necessary to engage properly the tug-mounted ram assembly with the barge.
It is yet another object of the present invention to provide a simplified retraction brake for the coupling assembly which is non-rotating.
One other object of the instant invention is to eliminated the need in the prior art to use the screw drive to rotate the ram for alignment of the ram head with the barge channel.
The above objects are accomplished through an extending screw type coupling assembly that includes a two-portion ram associated with the screw, and a load cell associated with the screw. As described above with reference to the prior art, the coupling assembly of the instant invention includes a pair of axially aligned ram assemblies mounted to a pusher boat. The pusher boat is navigated into a stern notch of a barge. The rams of the ram assemblies are extended into channels or cavities bilaterally positioned within the stern notch through rotation of actuator screws connected to the rams. As the rams come into engagement with the barge, extension of the rams through rotation of the actuator screws is terminated. The load cell of each assembly is then activated to provide the engagement force necessary to securely couple the tug and barge.
The ram component of each assembly comprises two portions. The first portion of the ram, which is the drive brake portion, is in threaded connection with the actuator screw. The drive brake portion of the ram assembly works in combination with the screw to prevent axial movement of the ram assembly, and to transfer the engagement force from the ram through the screw and ultimately to the tug hull upon engagement of the ram with the barge. As an axial force is applied to the ram by engagement with the barge, a motor brake, or other suitable screw brake, will prevent any rotation of the screw that might be caused by the engagement force; thus working in combination with the screw and the drive brake portion of the ram assembly to act as a drive brake for the entire assembly. The second portion of the ram, the piston portion, is capable of rotational movement relative to the drive brake portion.
The instant invention is referred to as a drive brake because rotation of the screw drive is terminated to activate the brake. As opposed to the prior art retraction brake discussed above, the to inventive drive brake is positive in that when activated it will statically prevent axial movement of the ram. When the actuator screw is rotated, the drive brake portion of the ram will move axially along the screw to extend and retract the ram; when the rotation is discontinued, axial movement of the drive brake portion of the ram is eliminated. The drive brake of the instant invention eliminates the need for a complicated control system and associated dynamic locking structure, reducing both the cost and weight of the assembly.
Because the drive brake is non-rotating, and the piston portion is rotatable with respect to the drive brake portion, relative pitch movement between the tug and barge is permitted without resulting in rotation of the actuator screw or drive of the ram assembly. This eliminates the need to declutch the drive motor to reduce inertia and results in a non-rotating drive to hull load transfer interface. Additionally, the non-rotating drive brake and rotating piston combination eliminates the torque forces on the actuator screw that are constantly present during engagement of the prior art retraction brake, reducing the wear on the ram assembly components.
Several embodiments of the instant invention are provided showing several possible locations of the load cell. In each of these embodiments the load cell works in combination with the actuator screw to provide engagement of the tug and barge. The actuator screw extends the ram into the channel on the barge; this alone will provide a secure connection between the tug and barge that can withstand a substantial amount of exterior forces incurred during tug-barge connection. Once the ram assembly has been extended into the barge channel, the load cell is activated to provide a tight engagement force between the tug and barge, thus increasing the strength of the tug-barge connection and minimizing the possible noise of the connection. The primary purpose of the load cell is to provide an engagement force rather than axial movement of the ram, thus the actual axial movement of the ram assembly caused by the load cell will be minimal. In this way catastrophic decoupling of the tug and barge is prevented in the event the load cell is depressurized because the actuator screw will maintain the connection.
In one embodiment of the instant invention, the axial movement of the ram assembly is accomplished through the use of a load cell positioned between the drive brake and the piston portions of the ram assembly. As the load cell is activated, the piston is forced away from the drive brake, forcing the piston into tight engagement with the barge. In another embodiment of the instant invention, the load cell is positioned between the housing of the assembly and the actuator screw. In this embodiment, as the load cell is activated, the actuator screw is forced to move axially with respect to the housing. As the actuator screw moves axially, so does the ram assembly through the movement of the screw.
The two piece construction of the ram, combined with the load cell, eliminates the prior art requirement for low speed motor 98 to extend ram 38 into tight engagement with the barge. Elimination of one of the two motors and all drive clutches results in substantial production cost savings and weight reduction, as well as elimination of the torsional engagement forces to which the actuating screw is subjected during engagement.
One other disadvantage of the prior art assembly that is overcome by the present invention is the need for a tensioning assembly to extend and retract lubrication lines and control cables that attach to the ram. Because the entire ram assembly of the prior art, including the retraction brake and actuator screw, is rotatable upon engagement with the barge, a tensioning mechanism is necessary to prevent binding of the lines and cables during rotation. This tensioning mechanism adds considerable weight and expense to the coupler assembly. The drive brake of the instant invention provides a non-rotatable mount for lubrication lines and control cables, eliminating the risk of binding and thus the need for a tensioning mechanism.
Another optional feature of the instant invention is the inclusion of a passage extending axially through the screw. In the instant invention the passage is used to provide lubrication to the ram assembly; however, the passage could be used for other purposes, such as providing connection of control lines to the ram. The instant invention utilizes an expandable tube for carrying the lubrication through the passage. The preferred embodiment of this tube is telescoping. This allows the tube to be both axially expandable as well as rotatable. Other forms of lubrication tubes may be utilized in the instant invention; however such may require additional mechanisms for extension and retraction of the tubes.